In the tire and rubber industry, calender lines process "gray" fabric for the purpose of producing laminate sheets used to construct rubber tires. The fabric includes longitudinally extending reenforcing cords spaced laterally across the fabric between two transverse edges, which cords are held together by transversely extending picks including small strands or threads spaced longitudinally of the fabric. The fabric is unrolled and then treated in the calender line in a manner that requires periodic spreading of the fabric to a width which is carefully controlled as the fabric enters the calender. The tire cord fabric is produced with various cord counts per inch across the fabric, i.e, cord distribution. In some instances, the cord count or distribution is as low as twelve cords per inch; however, it can be as high as thirty cords per inch. These fabric cords are held together by the picks, which are woven perpendicular in the cords and spaced along the fabric with 2-3 picks per linear inch of cord. From a quality standpoint, the objective is to have the desired cord count extending uniformly over the entire width of the fabric before the fabric is introduced into the calender. However this even distribution of the cords is not accomplished in calender lines now in use. The fabric has a tendency to neck down as it travels toward the calender; therefore, the fabric must be respread several times in the calender line. Spreading devices heretofore used are not predicated on the cord count. As the fabric is respread periodically during its travel through the line, a greater number of cords remain bunched at the edges because the spreading devices are ineffective in spreading this portion of the fabric. Thus, a high concentration of cords appear adjacent the edges of the fabric as the fabric enters the calender for rubberization even though the fabric has the proper width. After processing by the calender, the edge portions of the fabric must be removed by a continuous cutting operation that results in a large amount of scrap with a corresponding reduction in yield for the calender line. Typically, the outer three to five inches at the edges of the fabric are unacceptable because of an over concentration of cords. This particular problem has troubled the tire and rubber industry for many years. To date, the industry has not developed an automatic spreading device that controls the count of the cords across the fabric preparatory to the fabric entering the calender.
Static devices, such as spread bars, have been added to the calender line immediately adjacent the entrant end of the calender in an attempt to address the problem of the cords of the fabric grouping at the edge of the fabric. These bars have two to four indexed positions and they must be manually shifted as a different fabric is being processed. Such devices cannot control width, are not automatic and substantially increase labor costs and down time when changing fabric being processed in the calender line. The most common spreader immediately adjacent the calender is a three finger spreader. This device generally spreads to width; however, the cord count across the fabric is not controlled. Feedback arrangements for use on three finger spreaders are difficult to control and sometimes result in splitting of the fabric.
Bowed roll spreaders are commonly used to spread the fabric to the desired width. Indeed, four or five bowed roll spreaders may be used before the fabric enters the calender. The three finger spreaders are located six to eight feet beyond the last bowed roll spreader since a bowed roll spreader can not be located close to the calender. Consequently, the fabric necks down after the last bowed roll spreader and before it enters the calender itself. For that reason, there is a need for a spreader to control fabric width immediately adjacent the entrant end of the calender. The three finger spreader is the device which is now commercially acceptable. Since a three finger spreader at this location can cause breakage of the picks and/or cords when using a feedback control, a fixed three finger spreader has been used to approximate the desired width of the fabric as it enters the calender. The only way to actually distribute the cord is the previously mentioned spreader bar that can be located immediately before the calender. This device is so labor intensive that it is not widely used. The operator must spread the fabric over the face of the bar before the line can be continuously operated. The calender lay down roll cannot be cleaned without removing the bar; therefore, the operator plays a substantial roll in a line which uses a spreader bar for distributing the cords prior to the calender. Thus, only width control devices have been used routinely in the tire industry for a calender line.
The edge spreader system disclosed in U.S. patent application Ser. No. 09/114,374 filed Jul. 14, 1998 titled "Spreader for Calender Line" overcomes many of the problems of past edge spreaders. The edge spreader system incorporates the use of a mandrel have a surface with a plurality of grooves. The surface of the mandrel has a generally cylindrically shape with grooves formed by a helically shaped groove. The helical groove has convolutions having a pitch generally equal to the desired cord distribution laterally of the fabric. The mandrel is moved laterally toward the fabric and simultaneously rotated to capture the cords in the groove of the mandrel. The mandrel is rotated at a constant speed and moved laterally at a constant speed until the edge of the fabric is positioned in a desired position relative to the calender. An edge sensor and feedback control system are used to control the edge of the fabric relative to the calender. The edge spreading system can include an arrangement to engage two or more mandrels having different pitch grooves with the fabric so that different cord distributions in various fabrics can be easily processed by the edge spreader system.
Although the edge spreading system disclosed in U.S. patent application Ser. No. 09/114,374 is a significant advance and improvement over past edge spreading arrangements, the edge spreading system requires the bunching of the cords at the edge of the fabric prior to capturing the cords on the mandrel. If the cords at the edge of the fabric are not closely bunched together, the mandrel has a tendency to spread these cords farther apart than desired. However, if the cords at the fabric edge are bunched to closely together or overlap one another, the mandrel may not properly spread apart all of the cords at the edge of the fabric. In addition to problems with some cord distributions, the cords traveling in the grooves of the mandrel have a tendency to lift or pop out of the grooves as the fabric moves over the grooves resulting in uneven cord distributions. This lifting of the cords out of the grooves is caused by the picks in the fabric that hold the cords together.
In view of the deficiencies of the edge spreading system disclosed in U.S. patent application Ser. No. 09/114,374, there is a need for an improved edge spreader system that more accurately controls the fabric cord spacing and fabric position prior to the fabric entering a calender, and maintains the desired cord spacing.